(I put this together for a friend, who wanted to play the biggest, meanest bully around. It's all theorycraft, I've never used this in play, so I have no idea how good it is. If anyone can recommend ways to improve the build, or can comment on how useful it is, I appreciate it!)
The Barbaric Bully
"He's big, he's dumb, he's got the IQ of gum, he's got the brain about the size of a sourdough crumb! But he'll beat on your head, like a big-bass drum! His behavior is truly unruly; He's a Bully!"
—Phineas and Ferb, "He's a Bully"
There's a few ways to go about building a Barbaric Bully. The first choice to be made is that of race.
The Human Bully
The Human Bully is the easiest to build right out of the gate, thanks to the bonus Feat gained at first-level. You aren't going to need a lot of skill points, so lowering Intelligence to 8 won't hurt you much, thanks to the racial skill bonus.
The Half-Orc Bully
You're one Feat down, but Half-Orcs gain a +2 to Intimidate that mostly makes up for it initially. Further investment will get you the best possible Intimidate, but you probably don't need to go quite that far. Darkvision and the other racial traits are useful as well.
The Half-Elf Bully
This seems like an odd choice, but the free Skill Focus (for Intimidate, naturally) is almost as good as Intimidating Prowess by itself. You'll be doing some multiclassing, and the Half-Elf makes that hurt the least. Finally, the bonuses against enchantment is golden, as you're going to have a weak Will save.
Ability Scores
Strength: at least 16 post-racial is ideal. You shouldn't need more than this, but it certainly won't hurt.
Dexterity: you're going to be wearing medium armor, and possibly light, if you give yourself more Rogue levels. So at least 12, more if you can spare the points.
Constitution: you're likely to gain Rage at some point, and that means you're going to want at least 12 here. 14 is probably better.
Intelligence: your best dump stat. It means that you'll be very limited in skills at first, but Rogue levels can more than make up for this.
Wisdom: definitely don't dump this, and if you can spare a few points, the more the better. Again, Will saves are a weak point for you.
Charisma: depending on how soon you get Intimidating Prowess, you don't need a lot of Charisma. A 12-14 is probably more than enough.
Feats:
Weapon Focus: you really only need this as a prerequisite for Dazzling Display. If you plan on using Bludgeoner, take a bludgeoning weapon. The Warhammer will serve you well.
Dazzling Display: as a full-round action, you can use Intimidate to demoralize all enemies within 30'. This is your big dance number, and it's best to be used as soon as you can hit a large group of enemies.
Intimidating Prowess: think of this as part of the engine that powers the Barbaric Bully. Adding your Strength to Intimidate checks allows you to have higher Strength than Charisma. It won't do more than Skill Focus at first, but as you rise in level, it's going to get better and better, especially once Rage is on the table.
Bludgeoner: this lets you deal nonlethal damage with a bludgeoning weapon without penalty. By itself, it's only marginally useful, unless you want to take prisoners. However, it opens up a great combo with...
Enforcer: whenever you deal nonlethal damage with a melee weapon, you can attempt to demoralize the target as a free action. If you succeed, the target is shaken for a number of rounds equal to the damage dealt. If you score a critical, a successful demoralize shakens as above and frightens the target for 1 round. I can't stress how badass this Feat is. Taking it at first-level instead of Dazzling Display is quite possibly a better deal- but being able to demoralize groups of enemies is amazing as well.
Power Attack: this nets you some bonus damage, but the penalty to hit might not be worth it. The real reason to take this is...
Cornugon Smash: if you hit an enemy and gain the bonus damage from Power Attack, you can demoralize the target as a free action.
Skill Focus (Intimidate): should be self-explanatory.
Weapon Specialization: more damage.
Shield Focus: more AC. Dodge would be slightly better if you have the Dexterity for it.
Improved Initiative: especially once your build gets rolling, going first can become important, as you quickly become able to frighten enemies in one round.
Iron Will: your Will save sucks. This isn't going to solve your problems, but it can't hurt.
Traits:
Love Lost. Not only does it give you +2 Intimidate...your backstory writes itself! I'll copy the text here:
Someone you loved was knifed to death in a dark alley one night. You were called to the scene by the guard to identify the body, and as rough as that was for you, you also noticed a ring was missing from the body. Whoever murdered your loved one stole that ring—you’re convinced of it. You’ve done some investigation on your own and recently found the ring for sale at a local merchant. Although, to your great frustration, you can’t afford yet to buy it back, the merchant did tell you from whom he purchased the ring. It seems likely this criminal is the one who killed your loved one, or at the very least knows who did. The only problem is finding him.
Reactionary: +2 initiative is nice.
Strong-Willed: this will help with most of your Will saves.
Levels
For first-level, I suggest Fighter, with the Viking Archetype. The Viking gives up heavy armor and tower shields at first-level, and doesn't get anything at first to replace that, which is bad. But there are good reasons to pursue this Archetype.
Feats: Weapon Focus, Dazzling Display, Intimidating Prowess*
Skills: Intimidate
Second-level we move into Rogue. The Thug Archetype gives up Trapfinding, and you won't miss it. Instead you get what is probably the most important ability the Barbaric Bully can get.
Frightening (Ex): whenever a thug successfully uses Intimidate to demoralize a creature, the duration of the shaken condition is increased by 1 round. In addition, if the target would be shaken for 4 or more rounds, the thug can instead decide to end the shaken effect to make the target frightened for 1 round.
Frightened is a lot like shaken, except the target will flee you as best as they possibly can on their turn if able. This means they won't be attacking anyone, and they will very likely provoke attacks of opportunity as well.
You also get Sneak Attack, for a little bit of bonus damage.
Third-level, I suggest taking your second level of Fighter. This gives you Fearsome.
Fearsome (Ex): at 2nd level a viking can make an Intimidate check to demoralize an opponent as a move action.
At this point you probably have Enforcer, so you can potentially Intimidate the same enemy twice in a turn, much to his dismay.
Fourth-level. There's a few options here. Rogue 2 will net you Evasion, but keep in mind that's only useful if you plan on wearing light armor. As a thug, you get Brutal Beating, which lets you sicken enemies when you use Sneak Attack- which is nice, but Sneak Attack isn't a guarantee. You also get a Rogue Talent, though the best use of this feature is to get another Combat Feat (or Intimidating Prowess if you haven't gotten it yet).
Fighter 3 will get you Shield Defense, which increases your AC by 1 when you use a shield (as a Viking should!). Likely the better course of action.
Fifth-level. Fighter 4 will give your Viking the ability to Rage. Not bad, although a Barbarian level would give you more. On the other hand, if you're worried about your damage, Fighter 4 qualifies you for Weapon Specialization, which is another +2.
Sixth-level and beyond. At this point, it comes down to whichever class offers the more benefits. Past level 4, it's better to be a Barbarian than continue as a Fighter. More Rogue levels will net you skills and useful abilities, but you already have the important stuff.
If you do decide to become a Barbarian, I suggest taking a look at Drunken Brute. Being able to down a potion as a move action makes carrying around useful potions (Bull's Strength, Enlarge Person, Cure X) worthwhile.
How this works-
So the idea with this build is to demoralize your enemies. A lot. Normally, using Intimidate to demoralize is a standard action, but this build is based around getting more and better ways to accomplish this task.
At first, your choices are going to be “move and Intimidate” or “use Dazzling Display”. You might have to charge on occasion to get closer to enemies- that's ok. Not doing damage, even if you're applying a solid penalty to enemies isn't going to make the fight any shorter, after all. So don't be afraid to attack a weakened foe.
This gets easier at higher levels, when you have options to deal damage and scare your enemies spitless.
Demoralize: make an Intimidate check. The number you want is at least equal to the target's level/hit dice+Wisdom modifier+10. You'll note that many enemies have a fairly lower defense against Intimidate, which you can easily hit. This might make it seem like your insane Intimidate bonus is going to waste; I assure you, it's not.
When you succeed on demoralize, your opponent is shaken for one round, plus 1 round for every 5 points you beat their defense by. So, let's say you want to demoralize a level 2 Hobgoblin Warrior.
His defense is likely no more than 12-13. At level 1, you can easily have a +10 (or more!) Intimidate. On a roll of 10, you get a 20, which beats his defense by 5 points. This means he's shaken for 2 rounds.
This becomes important once you hit level 2 and get Frightening, which not only extends your durations, but gives you an important option to upgrade shaken to frightened.
Normally, fear effects stack, that is to say, if an enemy is shaken, if they are shaken a second time, they become frightened. If frightened, they become panicked. Intimidate cannot “improve” someone's state of fear by itself, so unless someone in your party likes fear magic, you're on your own.
Every full 4 rounds of shaken duration you would give someone lets you frighten them instead. So the faster you can do this, the better.
Another thing to note is that each time you demoralize an enemy, their defense against you increases by +5. Since it might take more than one attempt to frighten them, the higher your check, the better.
Example: at 2nd-level, you attempt to demoralize another Hobgoblin Warrior. You again roll a 10, beating his defense by over 5 (but not over 10). This would cause him to be shaken for 3 rounds (thanks to Frightening).
Next turn, you can demoralize him again. He currently has 2 rounds of being shaken. If you want to frighten him, you need to beat his defense by 5 or more. If you do, you make him frightened, and his next turn is going to suck.
By about level 3, you'll have multiple ways to demoralize in the same turn. With Enforcer, it's practically guaranteed that you will be able to frighten a target simply by hitting them (!). Then you can demoralize someone else as a move action (as long as they are within 30').
This might be all you need, making Cornugon Smash overkill. On the other hand, nothing stops you from hitting an enemy, using the free demoralize from Enforcer to frighten them, and then use Cornugon Smash to also render them shaken. This way, even when they come back, they'll still be shaken, and it'll be child's play to frighten them again.
It's worth noting some enemies will be immune to demoralize. Undead, constructs, plants, and vermin will be your big offenders here. Nothing you can do about it but just wade into melee and start smashing things. It sucks, but you'll still have good AC, hit points, and possibly the ability to rage.
Also, size matters. It's harder to Intimidate things bigger than you are. You should be able to handle the penalties, but Enlarge Person is a nice buff for you, so maybe invest in a potion or three!
Magic Items
Cruel Warhammer. A +1 is equal to a +2 weapon, so it's not cheap at first, but it's ability is golden. Basically, if you hit someone who is frightened or shaken with a Cruel weapon, they also become sickened for 1 round, just making their life suck more. This is something you want as soon as possible, so save up! If your GM likes to control how often you get magic items, smile sweetly at him and try to impress on him how much you really really want this!
Oh, as an added bonus, if you knock an enemy out with this weapon, you get 5 temporary hit points!
Circlet of Persuasion. A fairly inexpensive item that gives you +3 to Charisma checks. Like Intimidate.
Anything of Strength. With Intimidating Prowess, more Strength = better Intimidate.
Beyond that, the usual magical armor, shields, cloak of resistance, amulet of natural armor, and ring of protection will serve you well. Just try and get the good stuff as soon as you can. And don't forget potions, especially if you become a Drunken Brute.